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(Found the root cause) Outlook Pre-view slowness RRS feed

  • Question

  • https://social.technet.microsoft.com/Forums/office/en-US/8280389c-5878-4874-a135-9b8846fe1575/found-the-root-cause-outlook-preview-slowness?forum=outlook#82962e59-3154-48e7-a40d-b33f0a8393ba

    You can find related links from many users.
    Related link: https://social.technet.microsoft.com/Forums/en-US/f26f9941-66ca-4483-abf9-72b0a3b0229c/outlook-2016-on-exchange-preview-pane-slow?forum=outlook

    I found root cause of Outlook 2016 slowness, and it’s mainly related with Outlook security patch KB4475553.

    Wrap-up: When you open email, this patch makes Outlook check exchange server connection first, even though you are opening cached OST email, so I found there is always interaction of
    WAN latency. And this does not happen as long as  you are using pure version of Outlook 2016 or “work offline mode”. Also I guess it makes Outlook-process stuck when there is high
    traffic between PC and HK Exchange through WAN.
    And if you cannot find KB447553 from remove lists, then you should remove KB4484212 first.

    Details
    Office 2016 Slowness is mainly related with Outlook Security Patch.
    Pure version of Outlook Cache mode is not related Exchange Server Connection through WAN,
    but after update Outlook security patch, it’s checking Exchange connection whenever you open email no matter it’s cached OST or not.
    I have simulated under 3000ms legging on network, and found even OTS email takes 3 second to open.
    Also if I dropped inbound connection between PC and HK Exchange, and Outlook is stuck until open inbound connection again.
    This does not happen as long as you are using pure version of Outlook or Offline more with OTS. or using Non-cached mode.

    I believe Microsoft would fix this problem ASAP.
    Becaues after uninatall those security patch, I had to update KB311829 individually, because there is known bug not to save email body if you drag and drop email from Outlook to Desktop. Need Patch for Fix : KB3118293.

    Please fix the problem ASAP.
    Otherwise it causes Outlook unstable due to using Outlook without security patch.

    Thursday, June 11, 2020 1:26 AM